I have recently developed what sounds to be a grinding pulley noise on my 87 420sel, just broke 100000 miles. I have had the valve covers off and replaced those seals a 100 miles or so ago. At that time the timing chain guides looked OK, not sure if they were replaced but looked OK. The "grinding noise" I hear sounds to come from a pulley not internal. I am having trouble isolating it. The car starts and runs fine but the sound is constant. AC unit, failing water pump, fan clutch? Any help would be cool...
JD

You should grab a mechanic's stethoscope and have at it.

My 420SEL will occasionally growl from the alternator. As will my 300SD.

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I hear ya!
JD

I would ref mark the belt and remove to spin check each pulley individually .
Ad

Yeah, I understand it's a difficult problem to describe knowing the wide range of what a "grinding noise" could be. But a stethoscope, removing belt and spin pulleys by hand sounds to be the best bet. Thanks..
JD

Most likely the A/C idler pulley. Mark

I will check ac idler pulley 1st, thanks..
jd

jd, if your engine has a fan bearing bracket check that it rotates freely without excess play. On our 1991 300CE the fan bearing bracket failed, likely because the local indie overtightened the drive belt, and the pulley shaft wobbled causing a disconcerting, loud noise.

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Fred Hoelzle

Check you motor mounts.

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Found it! It's the fan. It seems to have a wobble and that is what is causing the "grinding noise". I guess this is just a replace part or can I just tighten it?
JD

is it the water pump bearing going out, or is the thermal coupling failing?

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jd, I'm not familiar with the V8 engines, but assuming the fan setup is the same as the straight 6-cylinder engines you will need to replace the fan bearing bracket. Based on my experience doing the replacement it's labor intensive with all that needs to be removed to access the fan bearing bracket.

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Fortunately the V8's don't have a fan bearing bracket. Mark

It seems to be the cooling fan clutch. Motor off, I can wiggle the fan by hand and feel and hear "play". Looks like four bolts secure the fan clutch assembly to the motor then the fan is bolted to the fan clutch. Ordered a new clutch and I'll post after install.
JD

I also started hearing a similar noise. I used a long wood dowel to pinpoint the source. I bit down on one end of the dowel then touched the other end to different points. The water pump is the source here. I can hear that sound and feel it too at the water pump and in the housing on top of the water pump. Dang!! $400 for a water pump. But it's less than my old car payment :-)

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